Permanent Magnet Motor Torque Ripple Reduction
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Solution Overview
Problem
Conventional permanent magnet motors experience significant torque ripples due to changes in the rotor core's outer diameter, leading to vibrations and noise, which are challenging to mitigate using existing methods.
Innovation Solution
The design incorporates a stator with annular core pieces and a rotor with embedded permanent magnets, featuring flange parts and connection portions where the width is adjusted to satisfy the condition 0.7 ≤ Wm/(Tm×Gm) ≤ 3.3, where Wm is the magnet's long side, Tm is the short side, and Gm is the maximum distance from the rotor's outer circumference, to reduce torque ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If recessed and projecting portions are formed at magnetic-pole switching portions to reduce torque ripple, then torque ripple is reduced, but manufacturing precision requirements increase and the structure becomes more complex
Solution Approach 1:
The patent changes the geometric parameters of the permanent magnets (width, length, thickness ratios) and their positional parameters (distance from rotor outer circumference) to optimize the magnetic flux distribution. By satisfying the condition 0.7 ≤ Wm/(Tm×Gm) ≤ 3.3, the torque ripple is reduced without requiring complex structural modifications like recessed portions, thus resolving the contradiction between torque ripple reduction and structural simplicity.
2Reliability
If the outer diameter of the rotor core changes due to mold wear, then the rotor surface position changes, but this causes great change in torque ripple with conventional configurations
Solution Approach 1:
The patent performs preliminary optimization of the permanent magnet dimensions and positions during the design stage. By pre-setting the magnet parameters to satisfy 0.7 ≤ Wm/(Tm×Gm) ≤ 3.3 and positioning them at specific distances from the rotor outer circumference, the system becomes inherently less sensitive to subsequent variations in rotor outer diameter caused by mold wear, thus maintaining stable torque ripple characteristics.
Solution Approach 2:
The patent optimizes the parameters of permanent magnets (width Wm, thickness Tm, position Gm) to create a design that is robust against variations in rotor outer diameter. This parameter optimization ensures that even when the rotor outer diameter changes due to mold wear, the torque ripple remains stable.
3Object-generated harmful factors
If permanent magnets are positioned to reduce torque ripple, then torque ripple is reduced, but the motor output torque may be affected
Solution Approach 1:
The patent optimizes the parameters of permanent magnets (width Wm, thickness Tm, position Gm) to create a design that is robust against variations in rotor outer diameter. This parameter optimization ensures that even when the rotor outer diameter changes due to mold wear, the torque ripple remains stable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively minimizes torque ripples, ensuring a stable and quiet operation by optimizing the size and placement of the permanent magnets and connection widths, achieving a torque ripple reduction of 0.5% or lower for the 48-th and 96-th components.
Implementation Method 1
a plurality of permanent magnets are embedded in a rotor so as to be adjacent to each other in the circumferential direction of the rotor
Implementation Method 2
an abrupt change in magnetic flux density occurs
Data Source
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AI summary
It has been discovered that torque ripples can be reduced by adopting a shape in which: the width of a shoe connection formed in a stator of a permanent magnet motor is equal to or smaller than the thickness of each of core pieces constituting a stator core; and a relationship of 0.7 ≤ Wm/(Tm×Gm) ≤ 3.3 is satisfied, where Wm is the length of the long side of a flat plate-shaped permanent magnet embedded in a rotor, Tm is the length of the short side of the permanent magnet, and Gm is the maximum distance from the outer circumference of the rotor to the permanent magnet.